The findings suggest that there are hundreds of deaths and many more costly illnesses each year from health problems that breast-feeding may help prevent. These include stomach viruses, ear infections, asthma, juvenile diabetes, Sudden Infant Death Syndrome and even childhood leukemia.

The magnitude of health benefits linked to breast-feeding is vastly underappreciated, said lead author Dr. Melissa Bartick, an internist and instructor at Harvard Medical School. Breast-feeding is sometimes considered a lifestyle choice, but Bartick calls it a public health issue.

Among the benefits: Breast milk contains antibodies that help babies fight infections; it also can affect insulin levels in the blood, which may make breast-fed babies less likely to develop diabetes and obesity.

The analysis studied the prevalence of 10 common childhood illnesses, costs of treating those diseases, including hospitalization, and the level of disease protection other studies have linked with breast-feeding.

The $13 billion in estimated losses due to the low breast-feeding rate includes an economist's calculation partly based on lost potential lifetime wages: $10.56 million per death.

The methods were similar to a widely cited 2001 government report that said $3.6 billion could be saved each year if 50 percent of mothers breast-fed their babies for six months. Medical costs have climbed since then, and breast-feeding rates have increased only slightly.

About 43 percent of U.S. mothers do at least some breast-feeding for six months, but only 12 percent follow government guidelines recommending that babies receive only breast milk for six months.